Chemical mechanical polishing is widely used in the manufacturing of semiconductor devices to obtain a smooth and even surface of the wafers. Typically, the wafer to be polished is held by a carrier positioned on a polishing pad attached above a rotating platen. By applying slurry to the pad and pressure to the carrier, the wafer is polished by relative movements of the platen and the carrier. A conventional polishing pad used in the chemical mechanical polishing process generally comprises a multitude of fine holes having a diameter of not greater than 200 microns. The holes can exhibit a pumping effect when pressure is applied to the polishing pad to achieve a high removal rate. However, after prolonged use, the holes can wear out or become blocked with polishing residues, causing an uneven surface of the polishing pad. As a result, the ability to polish wafers decreases over time and the effectiveness of CMP process for achieving a uniformly smooth wafer surface can be diminished.
To recover the polishing performance and to compensate for the uneven surface of the polishing pads, a conditioning process utilizing a conditioner for removing the uneven surface of the polishing pads is commonly used along with CMP processing.